1. Field of the Invention
The present invention relates to an information reproducing apparatus applicable to a reproducing apparatus that performs a Viterbi decoding process and a reproducing method thereof, in particular, to a detection of a phase error of a PLL.
2. Description of the Related Art
In a digital signal reproducing apparatus, a PLL (Phase Locked Loop) is used to generate a clock signal that synchronizes with a reproduced digital signal. Conventionally, an edge of a reproduced signal is detected. With phase information of the edge, a phase error is detected. With the detected phase error, the frequency of a VCO (Voltage Controlled Oscillator) or a VFO (Variable Frequency Oscillator) is controlled. Thus, the PLL generates a clock signal that synchronizes with the reproduced signal.
However, when a reproduced signal includes noise of 1/2 T or larger, since the noise tends to fold back, the PLL may get disordered and thereby a malfunction such as a bit slip may take place.